The disclosed embodiments generally relate to serial digital communication systems, and in particular, to a combination Inter-Integrated circuit (I2C) and serial to parallel (SPI) system.
Both the I2C and SPI communication protocols provide on-chip capabilities which allow compatible devices to communicate directly with each other. The I2C and SPI systems both provide serial communication between a master unit and slave unit, but use different signals and different protocols. An I2C bus typically utilizes two signal lines, serial data (SDA) and serial clock (SCL), for serial bi-directional data transfers. An SPI bus typically utilizes four signal lines, slave select (SS), serial clock (SCK), Master Out/Slave In data input (MOSI), and Master In/Slave Out data output (MISO), for serial bi-bidirectional transfers. The busses have different configurations and operate with different protocols. As a result, an electronic device configured with an I2C interface is required for use in a system with an I2C bus, and the equivalent electronic device must be configured with an SPI interface in order to operate in a system with an SPI bus. For example, an LCD driver coupled to an I2C interface is not usable in an SPI based system and the LCD driver coupled to an SPI interface is not usable in an I2C based system. It would be advantageous to provide an interface that allows an electronic device to be selectively coupled to both an I2C and an SPI communication system.